Buffer.java

/*
 * Buffer.java February 2001
 *
 * Copyright (C) 2001, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 
 * implied. See the License for the specific language governing 
 * permissions and limitations under the License.
 */

package org.simpleframework.util.buffer;

import java.io.IOException;

/**
 * The <code>Buffer</code> interface represents a collection of bytes that can
 * be written to and later read. This is used to provide a region of memory is
 * such a way that the underlying representation of that memory is independent
 * of its use. Typically buffers are implemented as either allocated byte arrays
 * or files.
 * 
 * @author Niall Gallagher
 * 
 * @see org.simpleframework.util.buffer.Allocator
 */
public interface Buffer extends Stream {

    /**
     * This method is used to allocate a segment of this buffer as a separate
     * buffer object. This allows the buffer to be sliced in to several smaller
     * independent buffers, while still allowing the parent buffer to manage a
     * single buffer. This is useful if the parent is split in to logically
     * smaller segments.
     * 
     * @return this returns a buffer which is a segment of this buffer
     */
    Buffer allocate() throws IOException;

    /**
     * This method is used to acquire the buffered bytes as a string. This is
     * useful if the contents need to be manipulated as a string or transferred
     * into another encoding. If the UTF-8 content encoding is not supported the
     * platform default is used, however this is unlikely as UTF-8 should be
     * supported.
     * 
     * @return this returns a UTF-8 encoding of the buffer contents
     */
    String encode() throws IOException;

    /**
     * This method is used to acquire the buffered bytes as a string. This is
     * useful if the contents need to be manipulated as a string or transferred
     * into another encoding. This will convert the bytes using the specified
     * character encoding format.
     * 
     * @param charset
     *            this is the charset to encode the data with
     * 
     * @return this returns the encoding of the buffer contents
     */
    String encode(String charset) throws IOException;

    /**
     * This method is used to append bytes to the end of the buffer. This will
     * expand the capacity of the buffer if there is not enough space to
     * accommodate the extra bytes.
     * 
     * @param array
     *            this is the byte array to append to this buffer
     * 
     * @return this returns this buffer for another operation
     */
    Buffer append(byte[] array) throws IOException;

    /**
     * This method is used to append bytes to the end of the buffer. This will
     * expand the capacity of the buffer if there is not enough space to
     * accommodate the extra bytes.
     * 
     * @param array
     *            this is the byte array to append to this buffer
     * @param len
     *            the number of bytes to be read from the array
     * @param off
     *            this is the offset to begin reading the bytes from
     * 
     * @return this returns this buffer for another operation
     */
    Buffer append(byte[] array, int off, int len) throws IOException;

    /**
     * This will clear all data from the buffer. This simply sets the count to
     * be zero, it will not clear the memory occupied by the instance as the
     * internal buffer will remain. This allows the memory occupied to be reused
     * as many times as is required.
     */
    void clear() throws IOException;

    /**
     * This method is used to ensure the buffer can be closed. Once the buffer
     * is closed it is an immutable collection of bytes and can not longer be
     * modified. This ensures that it can be passed by value without the risk of
     * modification of the bytes.
     */
    void close() throws IOException;
}